Analog-to-digital conversion is an electronic process in which an analog signal is changed, without altering its essential content, into a digital signal. Analog-to-digital conversion is performed using an analog-to-digital converter (ADC).
ADCs are used in a wide variety of electronic applications including, but not limited to, communications, imaging, measurement, control systems, sensors, etc. In general, ADCs may be used in any application in which it is desirable for an analog signal, i.e., a continuous electrical signal, to be digitally processed.
The converting of an analog signal to its digital counterpart is accomplished by repeatedly sampling a continuous analog signal, i.e., checking the voltage or current level at a fixed time, and outputting a digital approximation of each sample. The benefits of converting an analog signal to its digital representation include, but are not limited to, noise reduction and the ability to use computers and computing software to analyze and manipulate the signal, etc.
ADCs have numerous characteristics that may be altered depending on the particular purpose for which they are designed. These characteristics include sample rate, resolution, latency, power consumption, physical size, and cost. Sample rate refers to how often samples of the analog signal are made. Resolution refers to how many bits are used to represent the digital approximation of the analog signal for each sample. Higher resolution ADCs are capable of better digital approximation of the analog signal. Latency is the difference between the time an analog sample is acquired by the ADC and the time when the digital data is available at the output of the ADC.
As already stated, when implementing an ADC, the application normally determines which ADC architecture will be used. For example, while some applications may need high resolution, other architectures do not, but instead require a high sample rate. As presently understood in the art, a tradeoff exists between sample rate and resolution, i.e., the sample rate inversely affects the resolution and visa versa.
An exemplary application that requires ADCs with high sample rates is a wireless network. Wireless networks usually require ADCs that have high sample rates of at least 20 megasamples per second (MSPS). ADCs designed to work in wireless networks preferably consume little power and have low latency. They typically only need to be capable of moderate resolution.
Audio systems, on the other hand, typically only require ADCs with sample rates of 20-50 kHz. These ADCs may have moderate to high latency, but they usually have to be capable of high resolutions. Power consumption is not a stringent requirement in many audio systems.
Voice systems for use in cellular phone applications require ADCs that have even lower sample rates and resolution than do ADCs designed for use in audio systems. However, they preferably do not consume as much power as do ADCs in audio systems.
Wireless networks, audio systems, and voice systems are examples of the many applications that require ADCs with different characteristics. There are a variety of ADC architectures, each with different characteristics, that may be used for analog to digital conversion in these applications. These ADC architectures include, but are not limited to, pipelined ADCs, Sigma Delta (or Delta Sigma) ADCs, Successive Approximation Register (SAR) ADCs, Dual-slope ADOs, and Flash ADCs. Each of these ADC architectures is capable of different sample rates, resolutions, latencies, and power consumption. They vary in size and cost as well.
In developing a new electronic product or application that use ADCs, there are often several stages of testing, production, troubleshooting, etc., during which changes are made to the product that may affect the required characteristics of an ADC that is being used in the product. Changes in ADC characteristic requirements could result in the need to use a different ADC architecture than the one being currently used. It is often difficult, time consuming, and costly to change from one ADC architecture to another that has the desired characteristics. Thus, it is desirable to have a single ADC with characteristics that may be easily configured so as to emulate different ADC architectures.